Reinforcing process

ABSTRACT

The addition of fibrous polyester reinforcing material to rubber stock can be improved by treating the fibrous material with a polysulfonyl azide having the formula

United States Patent Inventor David S. Breslow Wilmington, Del. Appl.No. 862,520 Filed Sept. 30, 1969 Patented Oct. 26, 1971 AssigneeHercules Incorporated Wilmington, Del.

REINFORCING PROCESS 6 Claims, No Drawings US. Cl 161/231, 260/349 Int.Cl ..B32b 27/06,

CO7c 143/56 Field of Search 161/231,

[56] References Cited UNITED STATES PATENTS 2,254,191 8/1941 Roblin260/349 3,298,975 l/l 967 Feild et al. 260/349 Primary ExaminerDouglasJ. Drummond Attorney-Charles L. Board ABSTRACT: The addition of fibrouspolyester reinforcing material to rubber stock can be improved bytreating the fibrous material with a polysulfonyl azide having theformula R-(SO N where R is a polyvalent organic radical, such as analiphatic, cycloaliphatic or aromatic radical and x is an integergreater than 1. Vulcanized rubber tires reinforced with treatedpolyester tire cord are disclosed.

REINFORCING PROCESS This invention relates to a process of improving theadhesion of fibrous polyester reinforcing material to rubber stock andto the products so produced. In particular, this invention relates to aprocess of improving the adhesion of polyester fiber, including yarn,fabric and cord to rubber stockby-treatment of the fiber with apolysulfonyl azide and to the products so produced.

It is known to reinforce rubber products with various types ofreinforcing materials such as rayon, nylon, glass, and metal fibers. ltis also known that polyester fibers are advantageous because of theirhigher initial modulus, low elongation, greater strength retention underhumid conditions, and other improved properties. However, development inthe use of polyester fiber has been slowed by the problems of achievinggood adhesion between the fiber and rubber stock.

Now, inaccordance with this invention it has been found that polyesterfiber, including yarn, fabric, cord and the like, having good adhesionto vulcanized rubber stock can be prepared by modifying the fiber with apolysulfonyl azide as described hereinafter. The fiber-to-rubberadhesion can be further improved for some usages if an adhesive coatingis applied to the modified fiber. The coating frequently used in adispersion of a phenol-aldehyde condensation copolymer (i.e. resin) anda vinylpyridine containing rubber polymer latex. The modified polyesterreinforcing material of this invention can be used in any type of rubbertire, including automobile, truck, tractor, and aircraft tires, as wellas in rubber belting and rubber hose where low elongation, strength anddimensional stability are important;

The polyester fibers useful in the instant invention are made from thewell-known polyesters obtained by reacting .glycols, such as ethyleneglycol, propylene glycol, cyclohexanedimethanol, and the like withdicarboxylic acids, such as terephthalic acid, isophthalic acid,stilbene dicarboxylic acid, and the like. ln addition to the yarn,fabric or cord made from polyester fibers, combinations or blends ofpolyester fibers with, for example, cotton or rayon fibers can be usedin this invention. Improved adhesion of the polyester fibers to rubbercan be obtained by the process of this invention, no matter what thephysical form of these fibers. However, as a practical matter the fibersso treated generally will *havebeen previously plied or twisted intoyarn or cord or may have been woven or knit into fabrics. Thus, thisprocess is not limited to the treatment of tire cord. Various methodsfor the preparation of yarn, cord, fabrics and otherwoven or unwovenfibersubstrates are well known to those skilled in the art.

The polysulfonyl azides used to treat the polyester fiber in accordancewith this invention arerepresented by the formula where R is apolyvalent organic radical selected from aliphatic, cycloaliphatic, andaromatic radicals and x is an integer greater than 1, preferably fromabout 2 to 5. In preferred embodiments of this invention R will be anorganic radical selected from the group consisting of radicals derivedby the removal of two or more hydrogen atoms from alkanes, such as, forexample, ethane, propane, butane, isobutane, pentane and its isomers,hexane and its isomers, octane and its isomers, dccane and its isomers,dodecane and its isomers, octadecane and its isomers, and the like;cycloalkanes, such as, for example, cyclopropane, cyclobutane,cyclopentane, cyclohexane, cyclooctanc, and the like; alkylcycloalkanessuch as, for example, ethylcyclohexane, methylcyclobutane, and the like;aromatic hydrocarbons, such as, for example, benzene, naphthalene,biphenyl, and the like; alkyl-substituted arylenes, such as, forexample, toluene, ethylbenzene, mand p-xylene, 0-, mand p-diethylbenzeneand the like; diarylulkylenes, such as, for example, diphenylmethane,l,2-diphenylethune, l,l-diphenylpropane, l,3-diphenylpropane, 2,2-diphcnylpropane, and the like; dialkylcycloalkanes, such as, forexample, l,2-, l,3- and l.4-dlmethylcyclohexane, 1,2- and1,3-dimethylcyclopentane and the like; and the alkyloxyalkanes,aryloxyarylenes, alkaryloxyarylenes, alkaryloxyalkarylenes,aralkyloxyalkanes, aralkyloxyaralkanes, and the like; as well as thecorresponding thioand sulfonyl compounds, specific examples of whichinclude diethyl ether, propyl butyl ether, diphenyl ether,oxy-bis(p-methyl benzene), dibenzyl ether, diethyl sulfide, diphenylsulfide, dibenzyl sulfide, dibutyl sulfone, and the like compounds; andthe foregoing compounds with fluoro, chloro, bromo, and iodosubstituents. It will of course, be obvious to those skillled in the artthat R can contain other functional groups, which are substantiallyinert to the reactions in which these compounds are used, such asesters, amides, etc.

Typical compounds represented by the foregoing generic formula include1,9-nonanedisulfonyl azide 1,5-pentanedisulfonyl azide l, lO-decanedisulfonyl azide 1,3-benzenedisulfonyl azide2,7-naphthalenedisulfonyl azide l-octyl-2,4,6-benzenetrisulfonyl azide4,4"diphenylmethanedisulfonyl azide 4,4-diphenyletherdisulfonyl azideincluded with the above typical compounds are the mixed isomers ofchlorinated aliphatic polysulfonyl azides, such as the mixed isomers ofthe C to C aliphatic hydrocarbons substituted with an average of lchlorine and 2.5 sulfonyl azides per aliphatic chain.

The first step in the process of this invention is the modification ofpolyester fiber by treatment with a polysulfonyl azide. This isaccomplished by contacting the fiber with the polysulfonyl azidecompound as for example, by dipping, spraying, brushing, or runningit-over a coated roll with a dispersion or solution of the polysulfonylazide in a suitable liquid. Exemplary of suitable organic solvents forthe polysulfonyl azides are methylene chloride, trichloroethylene,methyl ethyl ketone, benzene and toluene. Water can also be used, withthe polysulfonyl azides being applied as an aqueous suspension, emulsionor dispersion. in the next step of the process, the thus treated fiberis heated to a temperature above the decomposition point of the sulfonylazide groups resulting in surface modification of the fiber. Thistemperature willin general be from about C. to about 250 C. Variousamounts of the polysulfonyl azidetreating agents can be used. Theoptimum amount will-depend upon the amount of modification desired, andthe specific polysulfonyl azide compound used. in general, the amountadded based on the fiber will be from about 0.1 to about 5.0 percent byweight. Next, the modified fibrous material may be coated with astandard'industrial coating, or adhesive, which is compatible with therubber in which the fibrous reinforcing material is to be'embedded. Asstated above, the coatingis generally a mixture of a'phenol-aldehyderesin and a vinylpyridine polymer latex: In all cases theexact selectionof the polymer latex components will be made to achieve compatibilitywith the rubber used in the final fiberto-rubber composite. Preferably,the phenol-aldehyde resin will be prepared from resorcinolandformaldehyde, although other phenols such as hydroxybenzene,para-cresol, and pyrogallol can also be used. The mole ratio of phenoliccompound to aldehyde inthe phenol-aldehyde resin can be varied betweenabout'lzl.02 to about l:5. The phenol-aldehyde resin will generallybeaged for a period of from about 0.5 to about 6 hours before mixingwith the vinylpyridine polymer latex. The said aging can be carried outat room temperature or elevated temperatures. For use with naturalrubber and styrene-butadiene rubber the.vinylpyridine polymer latex willpreferably be a terpolymer of a vinylaryl monomer, a diene monomer. anda vinylpyridine monomer. The winylaryl monomer will preferably bestyrene, although other monomers such as vinyltoluene can be used. Thediene monomers which can be used in preparing the polymer latex are openchain conjugated diolefins, including for example, l,3-butadiene,isoprene, dimethyl-l ,3-butadiene, 1,2-diethyl-l ,B-butadiene, and

piperylene. The vinylpyridine monomers most useful in preparing thepolymer latex are alpha-vinylpyridine, S-ethyl- 2-vinylpyridine, and2-methyl-5-viny1pyridine, although other monomers such as5-butyl-1-vinylpyridine, 5-heptyl-2-vinylpyridine,6-methyl-2-vinylpyridine, 4,6-dimethyl-2-vinylpyridine, and2-methyl-4-vinylpyridine can be used. The vinylpyridine content of theterpolymer is usually from about 5 percent to about 25 percent, thevinylaryl monomer content from about 5 percent to about 35 percent andthe diene monomer content from about 50 percent to about 85 percent. Therubber polymer latex can be admixed with the phenol-aldehyde resin inratios of between about 2:1 and about 10:1. Following the mixing of thetwo ingredients the pH 'will generally be adjusted to about 9.5 to about10.5 using an inorganic base such as ammonium hydroxide.

The modified fibrous material can be coated with the conventionalcoating uniformly by dipping, spraying, running the material over acoated roll, or other conventional procedure. The coating will amount tofrom about 2 percent to about 10 percent by weight of the material. Thecoated material will then be cured for a short time such as from about 1to about 10 minutes at a temperature of between about 250 F. and about450 F. The cured coating is a hard polymer which is very adherent to themodified fibrous material and produces excellent adhesion between themodified material and conventionally vulcanized rubber. it may bedesirable in certain cases, to omit the latex coating, thereby directlyembedding the modified polyester fibrous material in a vulcanizablerubber stock and curing to obtain a reinforced rubber product. Suchproducts reinforced with modified polyester fibrous material aresuperior to products reinforced with nonmodified polyester fibrousmaterial, but exhibit a proportionate decrease in adhesive strength overthose reinforced with modified fibrous material and coated with theabovedescribed coating composition.

In the final step of the process of this invention the modifiedpolyester fibrous material is embedded in the vulcanizable rubber stockto be reinforced and then the stock is vulcanized. Conventionalvulcanization temperatures in the order of from about 275 F. to about350 F. can be used. The rubber stock in which the modified polyester canbe embedded includes natural rubber and synthetic rubbers such asstyrenebutadiene rubber, ethylenepropylenediene terpolymer rubbers,ethylenepropylene copolymer rubbers, polybutadiene, polyisoprene, andmixtures or blends thereof with suitable fillers, pigments,antioxidants, and cross-linking (i.e. vulcanizing) agents such assulfur, dicumyl peroxide, and the like.

The following examples will serve to illustrate the invention, all partsand percentages being by weight unless otherwise indicated.

EXAMPLE 1 Po1y(ethylene terephthalate) tire cord 1,000 denier andthree-ply under about 500 grams of tension is passed twice through atrough containing a 5 percent solution of 1,3- benzenedisulfonyl azidein trichloroethylene. The cord is next passed through two ovens inseries at 200 F. and 400 F. Residence times in the ovens are 65 and 54seconds respectively. The cord dip pickup is approximately 0.9 percentby weight.

The modified cord is next dipped in a resin latex prepared as follows:To a solution of 0.24 part of sodium hydroxide in 192.8 parts of wateris added 8.8 parts of resorcinol with continued stirring until acomplete solution is achieved. Then 12.2 parts of 37 percentformaldehyde is added. The solution is aged for approximately 5 hours atabout 75 C. and then added slowly to a mixture of 48 parts water and 195parts ofa commercial latex comprising a terpolymer of styrene, buradieneand vinylpyridine. The monomers being present in a ratio ofapproximately :70:15. The mixture is stirred slowly for 15 minutes andits pH adjusted to 10.3 using concentrated ammonium hydroxide. Theresulting gray-violet latex contains approximately percent solids. Thedisulfonyl azide modified cord is passed twice through a trough of theabovedescribed latex under a tension of 500 grams and then dried andcured for 54 seconds at a temperature of 430 F.

The thus-coated cord is then vulcanized with a rubber tire stock in theform of 3/8-inch H-specimens. The rubber tire stock has the followingformulation:

Compounds Parts Natural rubber (smoked sheet) Styrene butadiene rubberSemireinforcing furnace black Zinc Oxide 5 Stearic Acid 2 Polytrimethyldihydroquinoline 1 Heavy pine tar 0.5 Benzothiazoyl disulfide lTetramethyl thiuram disull'ide 0.1 Sulfur 2.6

The test specimens are cured for 45 minutes at a temperature of 307 F.After several hours conditioning at room temperature the H-specimens aretested according to the procedure of ASTM-D-2138-62T. An average (6 testspecimens) of 31 pounds is required to overcome the tire cord-rubberadhesion. A control specimen treated exactly the same as above exceptfor the disulfonyl azide treatment gives an average of 17 poundsrequired to overcome the tire cordrubber adhesion.

EXAMPLE 2 Vulcanized rubber tire stock is reinforced with poly(ethyleneterephthalate) tire cord exactly as described in example 1 except forthe dip in the resorcinol-formaldehye latex. Test specimens are preparedand tested exactly as described in example 1. Those specimens treatedwith the disulfonyl azide require substantially more pounds of force toovercome the tire cord-rubber adhesion than do the control specimens.

EXAMPLE 3 A conventional rubber tire stock is reinforced with modifiedand coated polyester tire cord exactly as described in example 1 exceptthat in place of the 1,3-benzenedisulfonyl azide is used1,9-nonanedisulfonyl azide. The cords sulfonyl azide dip pickup is 1.8percent by weight. The resulting product is tested as described inexample 1. An average (6 test specimens) of 38 pounds is required toovercome the tire cord-rubber adhesion. The control gives an average of17 pounds required to overcome the tire cord-rubber adhesion.

What I claim and desire to protect by Letters Patent is:

1. In a process of adhering fibrous polyester reinforcing material torubber stock the improvement of first contacting said fibrous materialwith a polysulfonyl azide having the formula wherein R is a polyvalentorganic radical and x is an integer greater than 1 and heating thethus-contacted fibrous material at a temperature sufficient tosubstantially decompose the sulfonyl azide groups on the polysulfonylazide.

2. The process of claim 1 wherein the polysulfonyl azide is1,3-benzenedisulfonyl azide.

3. The process of claim 1 wherein the polysulfonyl azide is 1,9-nonanedisulfony1 azide.

4. The process of claim 1 wherein the fibrous polyester reinforcingmaterial is poly(ethylene terephthalate) tire cord.

5. A fibrous polyester reinforcing material modified by reaction with apolysulfonyi azide having the formula azide having the formula wherein Ris a polyvalent organic radical, and x is an integer greater than I.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent: No- 3,616,199 Dated Qctober 26 1971 Inventor(s) David S. Breslow (Case 51) It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

F- Column 1, line 24,- "in" should read --is- Column 1, (formula) ofprinted patent;

"R(SO N X" should read R (SO N Column 3', line 4; "5butyl-l" should read5-butyl-2- the SAL)

TiOBliIf-LT GOT'IlSCHALK ED IJARD FLETCHER J Commie; sioner of Pa to nts

2. The process of claim 1 wherein the polysulfonyl azide is1,3-benzenedisulfonyl azide.
 3. The process of claim 1 wherein thepolysulfonyl azide is 1,9-nonanedisulfonyl azide.
 4. The process ofclaim 1 wherein the fibrous polyester reinforcing material ispoly(ethylene terephthalate) tire cord.
 5. A fibrous polyesterreinforcing material modified by reaction with a polysulfonyl azidehaving the formula R-(SO2N3)x wherein R is a polyvalent organic radical,and x is an integer greater than
 1. 6. A vulcanized rubber productreinforced with fibrous polyester reinforcing material said materialhaving been first modified by heating with a small amount of apolysulfonyl azide having the formula R-(SO2N3)x wherein R is apolyvalent organic radical, and x is an integer greater than 1.